This guide book is written for those who have little background knowledge of geology. It focuses on the geology of Wales that can be seen from a car, with the descriptions organized in relation to the main roads. The best outcrops are in the sea cliffs and on beaches, these are also described where they are easily accessible from a main road. Many examples of geological activity are illustrated along the roads and cliffs of Wales, including basin sedimentation and volcanic activity. The effects of plate tectonics in opening basins, folding and metamorphosing the rocks in two major continental collisions are recorded in the Welsh Mountains.
Wales is one of the classic areas of geology. It was here that over two centuries ago, geologists recognized and named the three earliest subdivisions of the Palaeozoic Era (from 570 to 410 millions of years ago). The First – Cambrian Period, is named after the Cambrian Mountains, The Second and Third – Ordovician and Silurian Periods, are named after ancient Celtic tribes of the region.